A woman who says police harassed her into making a statement about the death of journalist Phillip Cottrell was concerned that her sister should not find out what she said, a jury has been told.

Detective Constable Olivia Gibson was giving evidence in the High Court at Wellington today about having taken a statement from Renee Robinson-Stepien in February this year.

Ms Gibson said Renee and Sylvanna Robinson-Stepien had been reluctant and scared when police spoke to them on February 1 but it was explained to them that someone had died and anything they could say could be helpful. They agreed to go to a police station to talk to police.

The sisters were arrested at the weekend after failing to appear as witnesses at the trial of their cousin, Manuel Renera Robinson, 18, and Sylvanna's boyfriend, Nicho Allan Waipuka, 20.

Robinson and Waipuka have pleaded not guilty of murdering Mr Cottrell, 43, a year ago today. Mr Cottrell was attacked walking home in the inner city at about 5.30am after a night shift at Radio New Zealand.

He died from head injuries the next day.

The Robinson-Stepien sisters criticised police and said they were harassed and forced to make statements and that some of what was recorded in the statements was not true. The statements included what Waipuka is alleged to have said to his girlfriend Sylvanna Robinson-Stepien and what she told her sister about it.

Renee Robinson-Stepien had not wanted her sister to find out what she told police, Ms Gibson said.

In court today Ms Robinson-Stepien said police had tried to break into her house by putting an arm through a cat door, but Ms Gibson said she looked through the cat door to see if she could see anyone inside but did not put her arm inside.

She said she could hear people inside but it took a while for anyone to answer the door.

Police had gone looking for them because they had failed to keep an earlier appointment to meet police.